/Engine/Source/Editor/StaticMeshEditor/Public/StaticMeshEditorSubsystemHelpers.h
struct FStaticMeshReductionSettings
float
PercentTriangles
Percentage of triangles to keep. Ranges from 0.0 to 1.0: 1.0 = no reduction, 0.0 = no triangles.
float
ScreenSize
ScreenSize to display this LOD. Ranges from 0.0 to 1.0.